A cost segregation study has no IRS due date of its own: for property a calendar-year owner placed in service in 2026, it has to be finished before the 2026 return is filed for its result to be on that original return. A calendar-year partnership or S corporation files that return by March 15, 2027 (September 15, 2027 with Form 7004), and a calendar-year individual or C corporation by April 15, 2027 (October 15, 2027 on an extension, Form 4868 for an individual or Form 7004 for a C corporation); every one of those extensions is an extension of time to file, not to pay.
A cost segregation study splits a building's cost into 5-, 7- and 15-year property and the 27.5-year residential rental or 39-year nonresidential structure under §168(c), and that split is reported as depreciation, on Form 4562, with the return for the year the property was placed in service. A study finished after that return is filed cannot be added to the original return after it is filed, though an amended return (in one case) or Form 3115 can claim it; both routes are set out below.
What are the 2027 tax deadlines for real estate owners filing 2026 returns?
In 2027 the 2026 federal income tax returns of calendar-year real estate owners are due on four dates: March 15, 2027 for partnerships and S corporations, April 15, 2027 for individuals and C corporations, and, on an extension of time to file, not to pay, September 15, 2027 for partnerships and S corporations and October 15, 2027 for individuals and C corporations. Each date below is the statutory date moved to the next business day where it falls on a weekend or legal holiday (IRC §7503); none of the 2027 filing dates below moves.
| Date (2027) | Return or payment (calendar-year) | Where a cost segregation study fits |
|---|---|---|
| Friday, January 15, 2027: calendar-year individuals' estimated tax | The fourth 2026 estimated tax installment (Form 1040-ES) | A payment, not a filing deadline for a study. Whether a deduction a study is expected to produce changes the installment is a projection for the tax advisor, because a loss that §469 or another limit suspends does not lower the 2026 tax. |
| Monday, March 15, 2027: calendar-year partnerships and S corporations, or Form 7004 to extend | The 2026 Form 1065 or Form 1120-S, with the owners' Schedules K-1; Form 7004 is an extension of time to file, not to pay | A study on property the entity placed in service in 2026 has to be finished before the entity files for its depreciation to be on that original return and on the K-1s. |
| Thursday, April 15, 2027: calendar-year individuals and C corporations, or Form 4868 or Form 7004 to extend; also individuals' estimated tax | The 2026 Form 1040 or Form 1120, with any 2026 tax owed, which an extension does not postpone; the first 2027 estimated tax installment (Form 1040-ES) | A study on property the owner placed in service in 2026 and holds directly, not through a partnership or S corporation, has to be finished before the 2026 return is filed for its result to be on that original return. |
| Tuesday, June 15, 2027: calendar-year individuals' estimated tax | The second 2027 estimated tax installment (Form 1040-ES) | Property placed in service during 2027 is depreciated on the 2027 return, not the 2026 one. |
| Wednesday, September 15, 2027: calendar-year partnerships and S corporations on a Form 7004 extension, and individuals' estimated tax | The extended 2026 Form 1065 or Form 1120-S, if not yet filed; the third 2027 estimated tax installment | The last filing date on which a study can be on the original 2026 entity return and the K-1s. |
| Friday, October 15, 2027: calendar-year individuals on a Form 4868 extension and C corporations on a Form 7004 extension | The extended 2026 Form 1040 or Form 1120, if not yet filed | The last filing date on which a study can be on the original 2026 return of an owner on extension; after the return is filed, the routes are the ones in the Form 3115 section below. |
| Friday, December 31, 2027: calendar-year taxpayers placing property in service (ready and available for its intended use) | Not a filing date: the last day property can be placed in service to be depreciated on the 2027 return | The study on that property can be finished in 2028, before the 2027 return is filed. |
Which 2027 due date is the deadline for a cost segregation study on the 2026 return?
The deadline for a cost segregation study on the 2026 return is the date that return is filed, so for a calendar-year owner it is March 15, 2027 for a partnership or S corporation and April 15, 2027 for an individual or C corporation, or September 15, 2027 or October 15, 2027 respectively on a Form 7004 or Form 4868 extension of time to file, not to pay, with the study finished before the return is filed for its result to be on that original return. The study does not have to be finished in 2026 itself, as Does a Cost Segregation Study Have to Be Finished for 2026 Depreciation? explains.
Property is placed in service when it is ready and available for its specifically assigned function (Treas. Reg. §1.46-3(d)(1)(ii)), not on the closing date by itself. A rental the owner bought with tenants in place is usually placed in service by that owner at acquisition; one that needs renovation before it can be rented usually is not placed in service until it is ready, and the year it is ready decides which return the study belongs on. How that test applies to a rental is set out in Placed in Service by December 31: Calendar-Year Rental Depreciation and Cost Segregation for 2026.
What the study needs, and when to gather it, is in What Documents Does a Cost Segregation Study Need Before You File Your 2026 Return?: the closing or settlement statement, construction invoices or pay applications, a land-value source and, for a property already on a return, the depreciation schedule.
Why does a partnership or S corporation need its cost segregation study before its owners can file?
A partnership or S corporation needs its cost segregation study finished before it files its own 2026 return for the result to be on that original return, because the depreciation reaches the owners only through that return's Schedules K-1, so an owner's individual return cannot carry a study the entity has not reported. A calendar-year partnership (Form 1065) or S corporation (Form 1120-S) files that 2026 return and the K-1s by March 15, 2027, or by September 15, 2027 with a Form 7004 extension, which is an extension of time to file, not to pay.
For a partnership, the cost segregation study has to be finished before the partnership files that return for its result to be on that original return and on the partners' Schedules K-1, where each partner can use its share only within the partner's basis (§704(d)), at-risk (§465) and passive-activity (§469) limits. For an S corporation, the same timing holds for the shareholders' Schedules K-1, where each shareholder can use its share only within the shareholder's stock and debt basis (§1366(d)), at-risk (§465) and passive-activity (§469) limits.
A partnership itself generally owes no federal income tax, because its income and deductions pass through to the partners (§701), but a required partnership return filed after its due date, including extensions, generally carries a penalty for each partner for each month it is late, up to 12 months, unless the failure is due to reasonable cause (§6698); an S corporation that files late faces the parallel penalty under §6699.
A partner or shareholder who is a calendar-year individual and does not have the K-1 by April 15, 2027 can file Form 4868 for an extension of time to file, not to pay, to October 15, 2027, so the individual's 2026 tax is still due April 15, 2027 and is paid on an estimate.
A partnership return already filed without the study is not amended the way an individual return is: a partnership subject to the Bipartisan Budget Act centralized partnership rules (one that has not elected out under §6221(b)) files an administrative adjustment request under §6227 instead of an amended return; a partnership that elected out is amended through its partners' returns. The Form 3115 route below works on the partnership's own later return.
Can a cost segregation study still make the 2026 return on an extension?
A cost segregation study can still go on a 2026 return that is on extension and has not yet been filed, as long as the study is complete before that return is filed: a calendar-year partnership or S corporation on a Form 7004 extension files by September 15, 2027, and a calendar-year individual on Form 4868 or C corporation on Form 7004 files by October 15, 2027. The extension does not have to be for the study; any return still unfiled on extension can carry a study finished before it is filed.
Every extension is an extension of time to file, not to pay: the 2026 tax of a calendar-year individual on Form 4868 or C corporation on Form 7004 is still due April 15, 2027, and interest and late-payment penalties generally run on tax not paid by then. The payment made with the extension is therefore an estimate of the 2026 tax, which the tax advisor can make with or without the study's figures; a study that lowers the 2026 tax after the payment shows up when the return is filed.
An extension of time to file is filed by the original due date of the return it extends. For an individual whose extended return is still unfiled after its extended due date, how to file it, including whether a study goes on it, is a question for the tax advisor.
What happens when the 2026 return is filed without a cost segregation study?
When the 2026 return is filed without a cost segregation study, the study's result cannot be added to the original return after it is filed, but the missed depreciation can reach a later return through Form 3115 or, in one case, an amended return. Under the automatic change procedures of Rev. Proc. 2015-13 and section 6.01 of Rev. Proc. 2025-23, the missed depreciation is claimed on Form 3115 with no amended returns when the property has been depreciated on two or more filed returns, or on one filed return if the taxpayer placed it in service in the tax year immediately before the year of change (the year of the return the Form 3115 is filed with), and the taxpayer still owned the property at the start of the year of change and meets the other eligibility rules.
For property the taxpayer placed in service in the tax year immediately before the year of change, with one filed return, either Form 3115 with the current return or an amended return for that year, filed before the return for the following year (the year of change) is filed, is available. A property placed in service in the current year goes on the original return and needs no Form 3115.
Applied to a 2026 return filed without a study: a building the taxpayer placed in service in 2026 and still owned at the start of 2027 can use Form 3115 with the 2027 return, or an amended 2026 return filed before the 2027 return is filed, and a building the taxpayer placed in service in 2025 or earlier and still owns can use Form 3115 with the 2027 return when it has been depreciated on two or more filed returns and the taxpayer meets the other eligibility rules. Section 6.01 of Rev. Proc. 2025-23 is the IRS's list of automatic changes, and each route is set out in Form 3115 Cost Segregation Catch-Up Depreciation on Your 2026 Return.
How much bonus depreciation applies to what a cost segregation study finds on the 2026 return?
Bonus depreciation on the 5-, 7- and 15-year property a cost segregation study identifies is 100% for qualified property acquired after January 19, 2025, unless the owner elects out. Per IRS Notice 2026-11 the acquired-date test turns on the written binding contract, not the closing date: the acquired date is the latest of the date the contract was signed, the date it became enforceable under state law, the end of any cancellation period, and the date any contingency was satisfied (Treas. Reg. §1.168(k)-2(b)(5)(ii)(B)). This applies to a written binding contract, meaning one enforceable under state law that does not limit damages to a specified amount (for example through a liquidated damages clause); under a contract that is not binding in that sense, the acquired date is generally when the taxpayer has paid or incurred more than 10 percent of the total cost, excluding land and preliminary activities (Treas. Reg. §1.168(k)-2(b)(5)(iii) and (v)).
Self-constructed property, including property built for the taxpayer under a written binding contract entered into before construction began, is acquired when physical work of a significant nature begins; paying or incurring more than 10 percent of the total cost (excluding land and preliminary activities) is a safe harbor. Used property qualifies only if the taxpayer had not used it at any time before acquiring it and the acquisition meets the §179(d) purchase rules that §168(k)(2)(E)(ii) applies (for example, it was not acquired from a related party, by gift or inheritance, or with a carryover basis). The test is walked through in The January 19, 2025 Line: How the Acquired-Date Test Sets Your Bonus Depreciation Rate.
Qualified property acquired on or before January 19, 2025 stays on the TCJA phase-down: 20% bonus depreciation if it is placed in service in 2026 and none if it is placed in service after 2026, with certain long-production-period property and aircraft under §168(k)(2)(B) and (C) one year behind (20% if placed in service in 2027). Bonus depreciation applies only to property with a recovery period of 20 years or less, so it reaches the 5-, 7- and 15-year property but not the 27.5-year or 39-year structure, and land is not depreciable at all. How the contract date plays out on a 2026 return is in Cost Segregation and the January 19, 2025 Written-Binding-Contract Cutoff on Your 2026 Return.
When is a cost segregation study worth finishing before the 2026 return is filed?
A cost segregation study is worth it when three conditions hold together: the basis is large enough for the accelerated deductions to outweigh the cost of the study, the deduction is usable this year given the owner's passive-activity position, and the hold is long enough to survive recapture. All three, or the honest answer is no.
The filing calendar does not change those three conditions; it only decides which return carries the result. A study whose deduction §469 would suspend on the 2026 return still moves the depreciation, but it does not lower the 2026 tax, as Will Cost Segregation Help If My Rental or Short-Term Rental Loss Is Passive? explains. None of this is a reason to buy a property or to rush one into service for the deduction alone: the placed-in-service date follows when the property is actually ready for its use.
To check whether a study fits the property before the 2026 return is filed, start with ClickDrag Finance's cost segregation qualifier. The placed-in-service date and whether the deduction is usable are questions for your tax advisor. To compare who prepares the analysis and how, read the guide to the best cost segregation companies.
What is not yet known about the 2027 tax calendar?
The federal due dates in the table are known now, because they come from the filing rules of the Internal Revenue Code (§6072) and move only when a date falls on a weekend or legal holiday (§7503), but three things can still change a particular owner's date: an IRS disaster postponement for a covered area (§7508A), a fiscal tax year, and a state return, whose due dates this article does not cover. The dates reflect the law as of this article's date.
This article also states no 2027 inflation-adjusted dollar amount: those amounts for the 2027 tax year come from the IRS's annual inflation adjustments, and none of them moves a due date or the order in which a cost segregation study and the return have to happen.
For calendar-year Opportunity Zone funds and investors, the 2026 to 2028 dates, each with its primary source, are on the Opportunity Zone and cost segregation calendar.
Related: cost segregation on the 2026 return, and what still applies to a 2025 return filed without a study.
Frequently Asked Questions
What is the last 2027 date to file a 2026 return on time with a cost segregation study?
For a calendar-year owner the last day is the 2026 return's due date, with the cost segregation study finished before the return is filed for its result to be on that original return. For a calendar-year owner that is March 15, 2027 for a partnership or S corporation (September 15, 2027 on a Form 7004 extension) and April 15, 2027 for an individual or C corporation (October 15, 2027 on a Form 4868 or Form 7004 extension); each extension is an extension of time to file, not to pay.
Does any 2027 federal due date move for a weekend or holiday?
None of the 2027 federal due dates moves: the calendar-year dates for partnership, S corporation, individual and C corporation returns, on time or on extension, and for individuals' estimated tax installments (January 15, March 15, April 15, June 15, September 15 and October 15, 2027), all fall on business days. Under IRC §7503 a due date that falls on a Saturday, Sunday or legal holiday moves to the next business day, which is why some years' dates differ from the statutory day.
Can a partnership extend its 2026 return to finish a cost segregation study?
A calendar-year partnership can file Form 7004 by March 15, 2027 to extend its 2026 Form 1065 to September 15, 2027, an extension of time to file, not to pay, and a cost segregation study finished before the partnership files is then on that original return and on the partners' Schedules K-1, where each partner can use its share only within the partner's basis (§704(d)), at-risk (§465) and passive-activity (§469) limits.
What if the 2026 return was already filed without cost segregation?
The missed depreciation from a cost segregation study can be claimed on a later return through Form 3115, under the automatic change procedures of Rev. Proc. 2015-13 and section 6.01 of Rev. Proc. 2025-23, for a property the taxpayer placed in service in an earlier tax year and still owns and when the other eligibility rules are met. For a property the taxpayer placed in service in 2026 with only the 2026 return filed, an amended 2026 return filed before the 2027 return is filed is the alternative to Form 3115 with the 2027 return.
Does an extension give more time to pay the tax a cost segregation study could reduce?
An extension gives more time to finish a cost segregation study before the return is filed, but not more time to pay, because it is an extension of time to file, not to pay: the 2026 tax of a calendar-year individual on Form 4868 or C corporation on Form 7004 is still due April 15, 2027, so the payment then is based on an estimate of the 2026 tax.
